Field of the Invention
The present disclosure relates to rechargeable batteries using charge carriers comprising aluminum ions, and particularly batteries with reduced toxic components to minimize human health hazards and environmental damage.
Description of the Background
With an increase in interest in generating electricity from renewable energy sources such as wind and solar, it has become increasingly important to identify a viable battery storage system. Lead acid batteries, for instance, are the most widely used battery technology for grid storage owing to their low cost (about $100-$150/kWh). However, lead acid batteries have a comparatively low gravimetric energy density (30-50 Wh/kg) and a poor cycle life, between 500 and 1000 charge/discharge cycles, based on the low depths of discharge (50-75%). In addition, lead acid batteries have significant safety problems associated with handling and disposal, due to the presence of sulfuric acid and toxic lead components. Reports of increased lead poisoning and acid-related injuries among workers and children exposed to unsafe handling and disposal of lead acid batteries, have raised strong concerns over large-scale implementation of lead acid batteries as storage for electricity generated from renewable energy sources.
The search for economical alternatives for electrical storage that lack the environmental and health risks of lead acid batteries has not been successful. One alternative, sodium ion batteries, are estimated to reach a price of about $250/kWh by 2020, but the volumetric energy density of sodium ion battery technology is lower than that of lead acid batteries at less than about 30 Wh/L.
Another alternative, vanadium redox flow batteries, offer high capacity, long discharge times and high cycle life, but have relatively low gravimetric and volumetric energy densities, and are expensive due to the high cost of vanadium and other components. Liquid metal batteries on the other hand are based on ion exchange between two immiscible molten salt electrolytes, but must operate at high temperatures, up to 450° C., rely on a complicated lead-antimony-lithium composite for ion exchange, and such systems have problems of flammability and toxicity.